Remission and Transition of Female Urinary Incontinence and Its Subtypes and the Impact of Body Mass Index on This Progression: A Nationwide Population-Based 4-Year Longitudinal Study in China

Purpose: We estimated the remission and transition rate between urinary incontinence (UI) subtypes in women with UI and evaluated the impact of body mass index (BMI) on this process. Materials and Methods: A Chinese population-based longitudinal study was conducted. Women aged >= 20 years were included using a multistage, stratified, cluster sampling method. Self-reported data on demographics, medical history, and physiological and anthropometric information were collected. UI was identified using 2 questions about any leaking symptom of stress UI (SUI) and urgency UI (UUI) in the past 6 months. Predicted probabilities of UI subtypes were calculated using multinomial logistic regression. Results: Analyses included 5,189 women (mean age 52.6 years, mean BMI 23.8 kg/m(2)), of whom 98.5% were parous. The median followup time was 4.0 years. Overall, the annual remission rate of UI was 12.7% among adult women. Regarding UI subtypes, the remission rates for UUI and SUI were similar, but higher than that for mixed urinary incontinence (MUI; p<0.05). In total, 7.6% of SUI patients and 16.4% of UUI patients developed MUI, and 35.3% of MUI patients continued to report MUI after 4 years. For women aged >= 60 years with a BMI >= 24 kg/m(2) and MUI at onset, the predicted remission rate (95% CI) was only 0.32 (0.29-0.35), but the predicted probability of the MUI remaining reached 0.50 (0.46-0.54). Conclusions: The annual remission rate of UI was 12.7% among adult women. Women with a higher BMI had less remission and a higher predicted probability of MUI 4 years later.